Implementation of EUCA-4529.

- Add user-facing operation for reading vm types
- Add euca-describe-instance-types

Also relates to EUCA-223, EUCA-2764, EUCA-442.
Merge branch 'dev/grze/EUCA-4529' into testing

Conflicts:
	clc/modules/cluster-manager/src/main/java/com/eucalyptus/cluster/ClusterEndpoint.java